Blake Lively's Free-Flowing Hair Leads to Donut Shop Investigation

Blake Lively might want to look over the food handler's license test ... 'cause her free-flowing locks have put a Connecticut donut shop she helped out under a microscope.

Here's the deal ... earlier this week, Lively helped out a friend who owns a small donut shop in Wilton, CT -- working a mixer, putting out the sweet treats for customers and just generally doing down-to-earth, everyday kind of work.

Of course, some people online have a bone to pick with Lively ... and, they're pissed she didn't put on a hair net or a hat, or tie it back, while working and serving up the treats -- writing on social media about it, even calling the local health department.

A spokesperson for the Wilton Health Department tells TMZ ... they have received complaints about Blake working without a hair net on -- and, it's under investigation.

Unclear what kind of sanctions -- if any -- the shop could face if the investigation finds them in the wrong ... but, clearly some people are upset enough with Blake to legitimately reach out to the WHD.

Worth noting ... the shop's Yelp Page has been temporarily disabled because commenters flooded it with negative reviews after Blake made her cameo appearance there -- with Yelp explaining they're investigating "whether the content you see here reflects actual consumer experiences rather than the recent events."

Before comments were disabled, a few users did actually post about Blake's lack of a hair net ... so, it seems it was something people really noticed this time around.

While some may actually be mad about hair nets, it's safe to assume some are just happy to hate on Blake because of her legal battle with Justin Baldoni.

A source close to Blake tells us ... “The so-called complaints are from people who have never been there and who don’t even live in Connecticut. Targeting a lovely, small, family-owned business is a new low in the retaliation campaign."

Blake's haters called her a hypocrite just this week for a resurfaced interview where she admitted to improvising a scene where she grabbed her costar Henry Golding's balls during "A Simple Favor."

Only time will tell if the Wilton Health Department's investigation will prove sweet -- or if it's really just full of holes.